Clubs usually look for managers with proven winning history to avoid risks and ensure good results. Ferguson huge success meant United trusted his judgment but if that trust led to decisions based on friendships over actual ability it certainly played big part in club decline.
It is clear that to succeed long term favoritism must be avoided in important choices like hiring manager. Even so your hope for Manchester United is valid. Many feel that with right choices and focus on merit club can definitely bounce back.
To achieve the desired achievement, of course, you have to focus on the first goal, and the most important thing is that unity is prioritized in a decision taken within the club. And that achievement that Ferguson made during his heyday can certainly be used as a guideline for current managers at Manchester United, and the achievements obtained are not enough and require hard work and of course, you have to learn a lot from people who can advance the club in the past.